Method and apparatus for handling gases and vapors



Dec. 8, 1925- 1,564 7 c. G. SMITH METHOD AND APPARATUS Fc m HANDLING GASES AND vAPoRs Filed May 19, 1922 Patented Dec. 8, 1925.-

UNITED STATES.

PATENT OFFICE.

CHARLES G. SMITH, OF MEDFORD, MASSACHUSETTS, ASSIGNOR TO BA'YTHEON MANU- FACTURING COMPANY, OF CAMBRIDGE, MASSACHUSETTS, A COREORATION OF MASSACHUSETTS.

METHOD AND APPARATUS FOR HANDLING GASES AND VAPORS.

Application filed Kay 19, 1922. Serial No. 562,282.

To all whom "it may concern:

Be it known that I, CHARLES G. SMITH, a citizen of the United States, residing at Medford, in the county of Middlesex and State of Massachusetts, have invented certain new and useful Improvements" in Methods and Apparatus for Handling Gases and Vapors; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as Wlll enable others skilled in the art to which it.

pressure to a region of higher pressure without the employment or interposition of moving elements. This result is accomplished in its broader aspects by impellmg gas molecules in a given direction through energy or momentum derived from contact of the molecules with a heated surface. I a moving molecule contacts with a heated surface, it is immediately caused to rebound from such a surface at a higher rate of speed, this added momentum of the molecule being derived from heat energy abstracted from the heated surface. I provide aplun-ality of heated surfaces designed and located in such a manner that impelling movements in a given general direction are suc-. cessively imparted to the molecules. In ad-' dition these heated surfaces alternate with relatively colder surfaces so arranged with respect to the heated surface that impact ofthe molecules therewith causes them .to

rebound at a speed less thanthat of impact.

The hot and cold surfaces areso arranged with respect to the direction of flow of the gas that molecules contacting with the hot surfaces are'caused to rebound in the desired direction of flow and molecules contacting with the cold surfaces are caused to rebound in a direct-ion counter to the direction of flow. It is essential for the efficient and practical operation of this apparatus that the passages .or openings available for the flow of gas molecules in the desired direction shall have an effective width or diameter comparable with and not substantially greater than the length of path through which the molecule of gas will normally travel at the given pressure of the gas. It is desirable for the efficient o eration of such an apparatus thatthe distance available for the travel of gas molecules from the cold to the hot surfaces shall be sufficiently short to prevent any substantial mutual interference of the molecules, or, in other words, the distance should be such that the molecules on the average will strike the walls of the passages rather than impacting with one another. On the other hand, the distance separating the hot and cold surfaces should be substantially greater and of sufficient extent to permit molecules rebounding from the hot surface to impact with and impel colder molecules before impacting with the cold surface. or passing out of the region through the passages in the cold surface. Because of the manner in which the two regions function.

that is the region between the cold and' hot surfaces and-the next successive region between the hot and cold surfaces, they may be referred to respectively as a region of diffusion and a region ofconvection, or, more properly, convection and difl'usion. In the first region gas molecules difi'use through the passages or openings extending from the cold to the hot surface with a minimum of mutual interference; where as in the next following region of convection gas molecules have ample space for -mutual interference and'impact with one another to set up convection in the desired direction. a

The new method may be conveniently embodied in an apparatus adapted to increase the pressure of a gas in a plurality of stages, such an ap ara-tus comprising essentially a series of su stantially parallel hot and .cold surfaces, together with what may be termed a gas'valve for controlling the flow of gas initiated by the hot surfaces. In a relatively simple and efficient form of the invention, cold and hot plates are alternately disposed in the desired path of movement of the gas, adjacent cold and hot plates being insulated 'from one-another and separated by a diffusion space to substantiali ly preclude mutual interference of gas molein a similar manner and constituting a sec- 0nd stage of the pump, these plates being repeated for as many stages of the pump as may be desired. Extending through the cold and hot plates and forming in effect a gas valve are a series of relatively narrow slits or openings having an effective width, which is comparable to or less than the average free path of the molecules in the gas, these openings permitting the gas molecules to fiow in one general direc ion but to a substantial extent precluding a net flow of molecules-in the opposite direction so that a general flow of gas is caused in the direction of rebound of the molecules from the hot surfaces. Such an apparatus when employed as a gas pump theoretically and practically produces an increase of gas pressure in each of the successive stages of the pump. It must be evident to those skilled in the art that apparatus of this character is most easily constructed to func-' tion at ressures below atmospheric pressures and in what is commonly known as a vacuum. The fact that the average free path of a gas molecule decreases and shortens with increasing gas pressures may impose practical limitations upon the pressures which can be obtained with such an a apparatus or at which the apparatus can be efiiciently employed, it being understood in this connection that increased gas pressures require a closer spacing of the hot and cold surfaces and a smaller width or diameter of openings available for the passage of gas molecules in order to insure proper operation of the pump.

The new method and apparatus is particularlyus'eful in connection with the circulation of gas or vapor for refrigerating purposes, where it is desired to evaporate a liquid at a low absolute pressure'and then pump the liquid vapor to a region of higher pressure, where it may be condensed, iving offbeat, the condensed liquid then being returned to the evaporation chamber. The method and apparatus is also useful in connection with the total or partial exhaustion of vacuum tubes of various kinds employed in the electrical industry. In this case the apparatus may be conveniently used in conjunction with a vacuum pump of usual form.

The applications of the new method and apparatus above stated are known and. understood and it is undoubtedly true that the apparatus has a large number of other useful applications, even thou h such applications may not be fully un erstood and appreciated at the present time.

The accompanying drawing illustrates the .the sur faces.

embodiment of the present invention in a refrigerating apparatus of simple form. In

Referring to the accompanying drawings, I

the gas or vapor pump comprises essentially a series of hot surfaces indicated at 10 with a series of cold or relatively coolersurfaces indicated at 12. The desired direction of flow of the gas or vapor is indicated by the arrows and it will be evident that this direction of flow is the same as the direction of rebound of the gas molecules from the hot surfaces 10. The distance between each of the cold and hot surfaces when considered as moving in the direction of flow of the gas is relatively small and is comparable to the average length of path of the gas molecules.

These surfaces are insulated from one another to prevent any substantial transfer of heat from the hot to the cold surfaces through the employment of solid particles, which are arranged in relatively close proximity and break up the-free space between These particles may take the form of a loose mass of small particles of material interposed between the surfaces or they may conveniently be formed as slight projections upon thin metallic plates,- two or more plates being interposed between each set of cold'and hot surfaces, and having openings therein available for the passage .of gas molecules therethrough. Each of the cold and hot plates is provided, as shown in Fig. 2, with a series of radial openings or passages 14 which may be conveniently, although not necessarily, located in alinement with one another and which are narrow in width and not substantially wider than the length of path of the gas molecules at the given gas pressure employed. These openings or passages in the hot and-cold surfaces constitute essentially a valve for permitting the molecules in general to flow according to the direction imparted by the hot surfaces .but precluding any substantial net flow of molecules in the oppositedirection. As indicated in the drawings, the pump may conveniently comprise several stages, whici maybe denoted res ectively at A,'B, C, D,

this character will increase the pressure between stages by approximately twenty per cent if the absolute temperature ratio is 1.5 to 1, that is to say the pressure in the chamber A will be one-fifth greater than the absolute pressure in the evaporation chamber and the pressure in the chamber B will be one-fifth greater than the pressure in the chamber A, this process being repeated according to the number of stages of the pump. The upper limits of pressure winch may be reached with such an apparatus are determined by practical considerations, in other words, the width of the gas openings or passages and the separation of the cold and hot surfaces.

The hot surfaces, as indicated, may consist of a series of relatively thin metallic disks 22 which project radially from the outer periphery of a tube 23 of conducting material. If heat is imparted to the walls of the tube 23 it willflow outwardly through the material of the disk 22, maintaining the surface 10 at the desired temperature. ,This heat energy may be supplied by an electric heating coil, indicated at 24 as received within the tube, or by some other convenient source of heat energy, as an open flame. The cold surfaces are conveniently constituted by a series of disks 26, extending inwardly from the walls of an outer enelos ing shell 28 and insulated from the adjacent hotter disks, as previously described. These colder disks or plates 26 are at approximately the temperature of the outer shell 28 and the adjoining hot plates or disks are at approximately the temperature of the inner tube 23,the temperature ratio of the Lot and cold surfaces determining the rate of flow and the difference in pressures obtained in the several stages of the pump. The tube 23 may be conveniently surrounded with insulating material, indicated at 30, which prevents any direct transfer of heat from the walls of the tube to the cold disks 26. Furthermore the peripheral edges of the hot plates-are spaced away from the inner surface of the outer shell 2 8.v This'construction prevents any direct transfer of heat from the hot to the cold disks and permits the two surfaces to be maintained at a suit:-

. cient difference of temperature to cause the pump to function. The outer shell 28,

desired temperature causes a continuous fiow of liquic vapor in the general direction of the arrow through the several stages of the pump. This constant flow of liquid vapor with the consequent continuous evaporation of the liquid abstracts heat from the refrigerating chamber R in which the lower end of the shell 28 is inserted through a wall 45. This abstraction of heat from the re-' frigerating chamber is aided by the employment of fins 47 located'upon the exterior of the shell, as .indicated m Figs. 1 and 3.

Leaving the evaporation chamber 20, the liquid vapor with the heat stored therein is moved through the several stages of the pump at a constantly increasin pressure until it reaches the condensingc amber G.

Thereafter the vapor is condensed upon the walls surrounding the condensing chamber giving off heat which is dissipated through radial fins or heat conducting members 52, which may be exposed to a natural or artificial circulation of air at room temperatures. This condensed liquid is collected in a se-' ries of spiral troughs 54 and 56, which serve to deliver it to a return pipe 58 extending back to the evaporation chamber. The low-.- er or delivery end of the return pipe may be conveniently provided with a U-shaped portion 60 to collect a body of liquid and form a seal to prevent the vapor assing from one chamber to the other. i ith such a construction, by maintaining the hot surfaces at a temperature approximating 100 C. or the boiling point of water, it is "possible to cause aflow of liquid vaponthrough the several stages ofthe pump and to gradually increase the pressure of the vapor.

In this connection it-ma'y be noted that Fig. 1 of the drawings illustrates adecreasing separation separation may bedesi'rable, owing to the in-' creasing pressure of the gas or vapor in successive stages with a correspondingly shortened path through. which thegas molecules travel. In this connection, however, it should be understood that it is entirely possible to provide a separation between the cold and hot surfaces designed for the greatest pressure of the gas which will enable the .several sets of cold and hot surfaces to be separated by a'uniform distance.

From the foregoing description it will be evident to those skilled in the art that the underlying principle of the present invention resides in the conversion of heat energy directly into kinetic energy of the gas molecule with means for utilizing this energy in a manner to increase'thepressure of the gas. As stated heretofore, in order to utilize this conversion of energy it is essential that the openings or passages available for the passage of gas molecules shall not substantial-- ly exceed in their effective width or diamerection, that is the direction imparted by the hot surfaces, but preventing any substantial flow of molecules in the opposite di- 1 rection, or counter to the direction im arted by the hot surfaces. If the widt of these passages were such as to permit a substantial unrestricted flow of molecules in both directions, the heat ener y would be utilized merely in'causing a, ow .of molecules in all directions without any useful result being derived therefrom.

Although it is to be understood that the present invention as hereinbeforedescribed is not limited to the following theory of operation, it is believed that this theory as briefly outlined is substantially correct. The operation of the gas pump is based upon the velocities of gas molecules and the mean free path of the molecules. If a vapor pressure is assumed such that the mean free path 1 of the gas molecules at that pressure is comparable to IV, denoting the width of the slits or openings in the hot and cold plates with a separation of the plates less than or comparable to W, then, by a proper design and location of the hot and cold surfaces. a general movement of gas molecules in the desired direction can be secured. Molecules striking the'hot surface leave it with higher velocities than molecules striking the cold surface, such molecules rebounding from the hot surface, moving with a higher velocity than normal and serving to give a push in the same direction to molecules encountered in their flight. This general push or impelling movement in the direction of rebound preponderates and the gas density adjacent the cold surface is increased. This gas diffuses through the narrow slits in the cold and hot plates and is impelled onward in the same direction by another cloud of moving high s eed molecules which have rebounded from t ie next successive hot surface. In addition to a relatively close spacing between cold and hot surfaces insulated from one another, it is essential that the difference between hot and cold surfaces forming the convection n region shall be much greater than the length of the path 1 in order that high speed molecules can strike others and impel them upwardly. The comparatively narrow slits or passages having the width V comparable to the path 1 prevents the crowded molecules above the hot surfaces from surging back through. the slot in such a manner as to hinder the counter movement of molecules from the colder region. In other words, the hot surfaces constitute impelling elements for-causing the flow of gas molecules and the narrow slits or passages constitute means for permitting a diffusion of molecules from one region of convection to thenez'tt'while precluding an unrestricted flow of molecules in the opposite direction.

I claim:

1. In apparatus of the character described, a pump unit comprising a pair of plates disposed adjacent to each other in face to face relation, each said plate having an aperture registering with the aperture in the other plate and means whereby one of said plates is heated and whereby the other of said plates is cooled.

2. In apparatus of the character described, a pump unit comprising a pair of plates disposed adjacent to each other in face to face relation, each said plate having an aperture registering with the aperture in the other plate, means whereby said plates are thermally insulated from each other and means whereby one of said plates is heated and whereby the other of said plates is cooled.

3. In apparatus of the character described, a pump unit comprising a pair-of plates disposed adjacent to each other in face to face relation, each said plate having an aperture registering with the aperture in the other plate, means for housing said plates in a gas or vapor at a predetermined pressure and means'whereby one of said plates is heated and whereby the other of said plates is cooled.

. 4. In apparatus of the character described, a pump unit comprising a pair of plates disposed adjacent to each other in face to face relation, each said plate having an'aperture of predetermined width registering with the aperture in the other plate and means where by one. of said plates is heated.

5. In apparatus of the character described,

a pump unit comprising a pair of plates disposed adjacent to each other in face to face relation, each said plate having an aperture of a'width comparable with the mean free path of the gas or vapor molecules to be pumped, the apertures in said plates registering with each other and means whereby 7 one of said plates is heated.

7. An apparatus for handling gases and vapors comprising closely spaced cold and .hot' surfaces insulated from one another with passages for the movement of gas molecules from the re ion 0 mate the cold surface to the re ion opposite the hot surface, these passages being comparable in width to the effective length of path of the molecules at the gas pressure employed.

8. An apparatus for handling gases and vapors which comprises a hot surface normal to the general direction of flow of the gas, a relatively colder surface opposed thereto, and a passage available for the movement of gas molecules from the region opposite the colder surface to the region opposite the hot surface and having a width not greater than the mean free path of the molecules in the gas.

9. An apparatus for handling gases and vapors comprising a hot disk or plate, a rela- 'tively colder disk or plate in close proximity thereto and insulated therefrom, and a semovement of gas molecules to successive re 11. An apparatus lating the relatively small space separating the cold and hot plates, and passages for the gions enclosed by the pairs ofhot and cold plates.

for handling gases and vapors. comprising a series of cold and :hot glatea-each pair of cold and hot plates being isposed in close proximity to one another with a'substantially greater separation between hot and cold plates, means for insulating the relatively small space separating the vapors comprising closing casing, a series of dev ces,

cold and hot plates, passages-for the movement of gas molecules to successive regions enclosed by the'pairs of hot and cold plates, and means for maintaining a substantially constant temperature of the hot plates.

12. An apparatus for handling gases and a hermetically sealed eneach having substantially parallel hot and cold surfaces contained within the casing and separating regions of different pressure substantially less than atmospheric, each said device having an aperture in its hot surface regisfor maintaining tering with an aperture in its cold surface to provide a passage therethrough, and means an elevated temperature of the hot surfaces.

13. An apparatus for handling gases and vapors comprising a closed casing having inner and outer walls enclosing an annular space, a series of surfaces extending outwardly from the inner walls and a series of surfaces extending inwardlyvfrom the outer walls and alternating with the first mentioned series, the outwardly and inwardl extending surfaces being maintained at di ferent temperatures, and means for insulatingthe surfaces from one another to prevent a direct conduction of heat therebet-ween.

14. Apparatus of the character described having a fluid passageway, not and cold surfaces disposed transversely of said passageway at spaced intervals and facing in opposite directions, and a passage available for the movement of gas molecules pastsaid surfaces, the width of said passage being comparableto the mean free path of the gas molecules. I v

15?. Apparatus of the character described having a fluid passageway, perforated plates disposed transversely of said passageway at 4 spaced intervals, op ositely directed surfaces of recurrent. lates aving greater ability to interchange eat with the fluid than the other surface of the same plates. v

16. Apparatus of the character described having a fluid passageway, perforated plates disposed transversely of said passageway at spaced intervals, oppositely directed surfaces of recurrent plates having1 greater ability to interchange heat with e fluid than the other surfaces of the same plates, and means whereby certain of the plates may be heated and certain other of the plates may be cooled.

17. Apparatus of the character described having a fluid passageway, perforated plates disposed transversely of said passageway at spaced intervals, one set of recurrent plates havin greater ability to interchange heat a with the fluid on one side, and another set-of recurrent plates having reater ability to interchange heat with the fluid on the opposite side, and means whereby one setof plates ma be .heated and the other set of plates coo ed. V

18, Apparatus of the character described having a fluid passageway, perforated plates v disposed transversely of said passageway at spaced intervals, one surface of each plate havm greater ability to interchange heat with t e fluid than the other surface.

CHARLES G, SMITH. 

